spring mvc零配置启动

/**
 * 关键点，实现WebApplicationInitializer这个接口可以实现在tomcat初始化时调用其onStartup方法
 */
public class MyWebApplicationInitializer implements WebApplicationInitializer {

  @Override
  public void onStartup(ServletContext servletContext) {
    //初始化webApplicationContext
    AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
    context.register(AppConfig.class);
    context.refresh();

    //注册dispatcherServlet
    DispatcherServlet dispatcherServlet = new DispatcherServlet(context);
    ServletRegistration.Dynamic registration = servletContext.addServlet("app", dispatcherServlet);
    registration.setLoadOnStartup(1);
    registration.addMapping("/");
  }
}

@Configuration
@ComponentScan("xyz.oldz")
public class AppConfig {
}

@Controller
public class HelloController {

  @ResponseBody
  @RequestMapping("/hello")
  public String hello() {
    System.out.println("hello");
    return "hello world!";
  }
}

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>xyz.oldz</groupId>
  <artifactId>SpringWeb</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>SpringWeb Maven Webapp</name>
  <!-- FIXME change it to the project‘s website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-catalina -->
    <dependency>
      <groupId>org.apache.tomcat</groupId>
      <artifactId>tomcat-catalina</artifactId>
      <version>9.0.30</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-servlet-api -->
    <dependency>
      <groupId>org.apache.tomcat</groupId>
      <artifactId>tomcat-servlet-api</artifactId>
      <version>9.0.30</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.apache.tomcat.embed/tomcat-embed-jasper -->
    <dependency>
      <groupId>org.apache.tomcat.embed</groupId>
      <artifactId>tomcat-embed-jasper</artifactId>
      <version>9.0.30</version>
    </dependency>

  </dependencies>

  <build>
    <finalName>SpringWeb</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>